Uveitis refers to several ocular disorders characterized by intraocular inflammation, which in the aggregate are a major cause of visual loss and blindness in the United States. Intermediate uveitis, posterior uveitis, and panuveitis are generally the more severe forms of uveitis, with the highest risk of vision loss, often requiring long-term systemic treatment. The fluocinolone acetonide intraocular implant is a surgically implanted reservoir of corticosteroid designed to last approximately 2.5 years in order to provide long-term control of uveitis. The primary objective of the Multicenter Uveitis Steroid Treatment (MUST) Trial is to compare the efficacy of standardized systemic therapy versus fluocinolone acetonide implant therapy for the treatment of severe cases of non-infectious intermediate uveitis, posterior uveitis or panuveitis. Patients with active uveitis will be randomized, with a 1:1 allocation ratio, to treatment with either the fluocinolone acetonide implant or standardized systemic therapy consisting of oral corticosteroids and supplementary immunosuppressive drugs when indicated, according to standardized guidelines. The design outcome variable for the study is visual acuity;other outcomes include other aspects of visual function, success in controlling uveitis, retinal morphologic outcomes, quality of life, cost-effectiveness, and occurrence of potential ocular and systemic complications of uveitis and of therapy.